Trouble starting my 4.8 (again) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

yossarian19 · 03-16-2014, 03:56 PM

I had it running a few months back & it was fine, started up a little slow but it started. Then I had to get a little "cleaner" with the wiring, re wired it (again) and now no start.
Yesterday I tried to run it and found that after too much cranking the cylinders were gas-washed (based on lack of compression noise).
Today, I pulled the plugs and all 8 were fuel fouled to some degree. Cleaned the plugs with a brass brush & brake clean, put a few squirts of oil into each cylinder, pulled the fuel relay & spun the engine over a few times. Compression was / is restored. Ate lunch, went out, installed relays & tried to jump start it. No joy - but plenty of oil smoke. Confirmed spark on the front two cylinders of the driver's bank & decided to let the starter cool down.
So, I've got fuel & I've got spark and compression sounds good. Still no fire. I think I may have gone too heavy on the oil? Not sure if that would stop it from running but I don't know what else to think just now. Any ideas?
Always possible it's something like "bad MAF" or "gunked IAC", but don't want to throw parts at it blindly.

ls1nova71 · 03-16-2014, 04:28 PM

I've never had any luck cleaning fouled plugs the way you described. I would try new ones.

BR3W CITY · 03-16-2014, 06:01 PM

These ignition will burn through copper plugs, even tho copper still is recommended in performance apps. If one gets partially fouled, its all the way bad...no cleaning em.
New plugs and regap...also clear any misfire codes from the ecm that might want to limp it.

VATS is removed, correct?

yossarian19 · 03-16-2014, 06:08 PM

VATS is removed - I've had this ECM / engine running before.
I had iridium plugs installed. Hard getting it started the first go-round, this time, I fouled them. Cleaned, I'm getting the occasional power stroke & regular compression - but not starting.
I'm thinking I'll buy some Denso copper plugs, gap to .060" and give it a shot.

**LEEVON** · 03-16-2014, 06:43 PM

Get stock plugs and gap to factory recommendations.

solidaxel · 03-16-2014, 06:51 PM

Quote:

Originally Posted by LEEVON

Get stock plugs and gap to factory recommendations.

What does everyone like for plugs in the 5.3?

yossarian19 · 03-16-2014, 07:41 PM

I'd run the OE replacement Irridium plugs unless you have a good reason not to.

I put in some new plugs & got "closer" to running. After a little while trying, I pulled the plugs and found them coated in 5w30 and gasoline. Dammit. Left the plugs out, cranked the engine for 10-15 seconds, shot a tiny bit of brake clean in each cylinder. Shot the crud off of the (new) plugs with more brake clean, leaving the cylinders open to hopefully evaporate / drain. Class tomorrow, more fun with truck Tuesday.
Feels like a waste of a nice day out. Just dammit.

03-16-2014, 03:56 PM	#1
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	Trouble starting my 4.8 (again) I had it running a few months back & it was fine, started up a little slow but it started. Then I had to get a little "cleaner" with the wiring, re wired it (again) and now no start. Yesterday I tried to run it and found that after too much cranking the cylinders were gas-washed (based on lack of compression noise). Today, I pulled the plugs and all 8 were fuel fouled to some degree. Cleaned the plugs with a brass brush & brake clean, put a few squirts of oil into each cylinder, pulled the fuel relay & spun the engine over a few times. Compression was / is restored. Ate lunch, went out, installed relays & tried to jump start it. No joy - but plenty of oil smoke. Confirmed spark on the front two cylinders of the driver's bank & decided to let the starter cool down. So, I've got fuel & I've got spark and compression sounds good. Still no fire. I think I may have gone too heavy on the oil? Not sure if that would stop it from running but I don't know what else to think just now. Any ideas? Always possible it's something like "bad MAF" or "gunked IAC", but don't want to throw parts at it blindly. __________________ "Over my head" 1957 Chevy 3200, big rear window & 6 lug. Front disc, power steering, Vortec 4.8 / 4L60E swap, hydro boost brakes & patina.

03-16-2014, 04:28 PM	#2
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: Trouble starting my 4.8 (again) I've never had any luck cleaning fouled plugs the way you described. I would try new ones. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

03-16-2014, 06:01 PM	#3
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: Trouble starting my 4.8 (again) These ignition will burn through copper plugs, even tho copper still is recommended in performance apps. If one gets partially fouled, its all the way bad...no cleaning em. New plugs and regap...also clear any misfire codes from the ecm that might want to limp it. VATS is removed, correct? __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

03-16-2014, 06:08 PM	#4
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	Re: Trouble starting my 4.8 (again) VATS is removed - I've had this ECM / engine running before. I had iridium plugs installed. Hard getting it started the first go-round, this time, I fouled them. Cleaned, I'm getting the occasional power stroke & regular compression - but not starting. I'm thinking I'll buy some Denso copper plugs, gap to .060" and give it a shot. __________________ "Over my head" 1957 Chevy 3200, big rear window & 6 lug. Front disc, power steering, Vortec 4.8 / 4L60E swap, hydro boost brakes & patina.

03-16-2014, 06:43 PM	#5
LEEVON Moderator Join Date: Jul 2006 Location: Ozark, MO Posts: 4,888	Re: Trouble starting my 4.8 (again) Get stock plugs and gap to factory recommendations. __________________ '20 Silverado Trail Boss ~ '17 Tahoe ~ '79 K15 Sierra Grande ~ '76 Blazer 2wd ~ '71 Cheyenne swb ~ '55 Pontiac Safari ~'50 3100 bagged ~ '80 Wife ~ Late model kids

03-16-2014, 07:41 PM	#7
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	Re: Trouble starting my 4.8 (again) I'd run the OE replacement Irridium plugs unless you have a good reason not to. I put in some new plugs & got "closer" to running. After a little while trying, I pulled the plugs and found them coated in 5w30 and gasoline. Dammit. Left the plugs out, cranked the engine for 10-15 seconds, shot a tiny bit of brake clean in each cylinder. Shot the crud off of the (new) plugs with more brake clean, leaving the cylinders open to hopefully evaporate / drain. Class tomorrow, more fun with truck Tuesday. Feels like a waste of a nice day out. Just dammit. __________________ "Over my head" 1957 Chevy 3200, big rear window & 6 lug. Front disc, power steering, Vortec 4.8 / 4L60E swap, hydro boost brakes & patina.



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